The present invention relates generally to the concept of dimensional weighing to determine the charge required by a carrier for transporting a package or parcel, and more particularly to a dimensional weighing system suitable for use by a variety of shippers and carriers to determine accurate freight charges for packages or parcels that are considerably oversized in comparison to their actual weight.
A detailed description of the background and development of the concept of dimensional weighing, as well as the significant problems and disadvantages of prior art dimensional weighing systems, is set forth in the Background of the Invention portion of the specification in the first of the above noted applications, which is hereby incorporated herein by reference.
Briefly, the invention disclosed and claimed in that application is a dimensional weighing apparatus in which a measuring frame has three measuring arms extending from a common juncture along the three axes of a package or parcel which must be measured to determine the volume of the parcel when positioned adjacent the measuring arms with a corner of the parcel adjacent to the common juncture thereof. A plurality of optical emitters, such as LEDs, are evenly positioned along the length of the measuring arms, and either one or three optical sensors, depending on the particular embodiment of the invention, are positioned such that the sensor(s) respond to all emitters on the measuring arms that are not obscured by the parcel. A computer processing system determined the length of each of the dimensions of the package or parcel and calculates its volume, and then compares that volume with a predetermined threshold volume stored in a memory. This determines, firstly, whether the volume of the parcel is less than the predetermined threshold volume so that it can be shipped at a shipping charge based on the actual weight of the carton as determined by a suitable weighing scale, or is larger than the predetermined threshold volume and may therefore require that a dimensional weight be calculated on which a shipping charge is to be based. If the latter situation prevails, the computer processing system then compares the dimensional weight of the carton with the actual weight to determine which is larger to ensure than the shipping charge is based on the proper weight.
Two significant problems became evident with that dimensional weighing apparatus. One was that it was sometimes difficult or awkward to place a carton on the scale platform because of interference with the sensor support, which generally occupied space within or closely adjacent to the space occupied by cartons on the scale, especially large cartons. In view of the large number of packages and parcels that typically could be handled by a large shipper or carrier, anything that hindered rapid and accurate placement of cartons on the scale represented a serious problem.
Another problem was that the apparatus was relatively expensive in that a large number of emitters were utilized to provide a high degree of resolution of the optical sensing system in order to achieve a high degree of accuracy in the calculation of the volume of cartons. Thus, the dimensional weighing apparatus was not cost effective for medium or low volume shippers or carriers, with the result that they often either over or under estimated or charged, as the case may be, thereby either cheating themselves or their customers.
This problem was addressed in another dimensional weighing apparatus disclosed and claimed in the second above noted application Ser. No. 08,775,851, which apparatus has many similarities to that already described but with two significant differences. The optical sensing system was modified to provide a plurality of combined emitter/sensor units spaced along the measuring arm, each unit having an emitter and a sensor disposed immediately adjacent to each other so that light from the emitter would be reflected back to the sensor by the side of a carton placed on the scale platform. The number of emitter/sensor units so activated by the side of a carton could enable the computer processing system to calculate the linear dimensions of a carton. Another significant change was that the number of emitter/sensor units was greatly reduced from that in the previous apparatus by increasing the spacing between the units. Although this resulted in a loss of resolution and accuracy, the computer processing means could provide a sufficiently acceptable estimate of the volume of cartons that the apparatus could be utilized with reasonable accuracy for the majority of cartons encountered in the ordinary course of many shipping situations, thereby greatly reducing the cost of the apparatus. The computer processing system could also provide the operator with a visual indication of whether the volume of a particular carton was above or below a predetermined threshold volume, above which the operator could manually measure the carton and determine an accurate shipping weight, and below which he could use the actual weight of the carton as determined by the weighing scale and still be assured of obtaining a realistic shipping charge for the carton.
Thus, the apparatus of this application was easier to use in that the operator was able to place cartons on the scale platform without interference from any supporting structure, thereby considerably increasing the speed at which cartons could be disposed on and removed from the scale. Also, it was considerably more cost effective for medium and low volume shippers and carriers because the reduction in the number of emitters utilized greatly reduced the cost of the optical sensing system, even though additional sensors were utilized because they were less expensive than those used in the first described apparatus because they were much smaller and did not have a wide included angle of vision. These advantages, however, were obtained only at the cost of considerably less resolution of the optical sensing system and consequent less accuracy in the calculation of the carton volume.
Further effort to avoid the disadvantages of the above described inventions led to the development of a dimensional weighing apparatus disclosed and claimed in third above noted application Ser. No. 08/775,675, which did not utilize an optical measuring system for measuring the linear dimensions of a carton. Rather, it utilized a mechanical measuring system in which a movable contact member was disposed in each of the measuring arms in place of the optical emitters of the earlier invention, the contact members being driven from the free ends of the measuring arms toward the opposite ends until they contacted the adjacent faces of the carton, at which point the drive for the contact members reversed direction in order to drive the contact members back to a starting position. The drive for the paddles included an optical encoder which provided the computer processing system with data indicative of the dimension of each of the sides of the carton being measured, from which the computer processing system calculated the volume of the carton and then performed the same comparisons and other calculations as performed in the earlier inventions. This apparatus had the advantage of providing a high level of accuracy in the measurements of the carton dimensions, was easy to operate, did not impede the proper placement of cartons on the scale, and was relatively inexpensive in comparison to an optical measuring system having a comparable degree of accuracy. The major disadvantage of this apparatus was still, as with the earlier forms of the apparatus, that it required a measuring frame associated with a weighing scale, which involved a piece of equipment dedicated to the dimensional weighing function, which in turn required the commitment of a substantial capital outlay for a shipper or carrier to obtain the capability of performing dimensional weighing.
Thus, there remains a need for a dimensional weighing apparatus which avoids the disadvantages of each of the above described dimensional weighing apparatuses, and therefore is sufficiently economical to be cost effective for small to medium size carriers and shippers, is easy to use, has a high throughput rate and yet is as highly accurate in measuring cartons and determining the volume thereof as the dimensional weighing apparatus with the accurate optical measuring system.